Segmented elctrode

ABSTRACT

Disclosed is a vital sign monitoring system. The system comprises a segmented electrode forming an in-plane electrode array, wherein the electrode comprise a skin contacting skin adhering contact layer mounted on an electrode backing material, a deformation sensor arranged for identifying deformation information of the electrode, a signal processor arranged to receive a vital sign signal from the electrode and process the deformation information to remove artefacts from the vital sign signal, wherein the electrode comprises multiple electrode segments and wherein the signal processor is arranged to select that electrode segment that has a lowest deformation of all electrode segments of the electrode.

This application is the U.S. National Phase application under 35 U.S.C.§ 371 of International Application No. PCT/EP2017/079514, filed on Oct.16, 2017, which claims the benefit of European Application Serial No.16194297.4, filed Oct. 18, 2016. These applications are herebyincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to a vital sign measurement system andmethod in the wearable technology.

BACKGROUND OF THE INVENTION

The rising trend in ageing population, increases attention to health andwell-being and growing domain of at-home monitoring.

For example the Philips' Biosensor patch enables continuous homemonitoring of vital signs such as ECG, heart rate, respiration rate,skin temperature and activity. The clinical data is sent to andprocessed by a cloud based platform and supports the healthcareprofessionals in their clinical decision making. The Biosensor patch canprevent hospital readmissions by detecting health deterioration in thehome setting as early as possible.

Increase of physician and patient acceptance of such devices, however,requires device optimization.

One of the most important vital signs is the ECG (ElectroCardioGram).The electrical activity of the heart is sensed by monitoring electrodesplaced on the skin surface. The electrical signal is very small(normally 0.1 to 3 mV). These signals are within the frequency range of0.05 to 100 Hertz. Unfortunately, artefact signals of similar frequencyand often larger amplitude can reach the skin surface and mix with theECG signals. Artefact signals arise from several internal and externalsources. Internal or physiologic sources of artefact are: signals fromother muscles (electromyographic signals) and signals produced in theepidermis. External or non-physiologic sources of artefact are: 50 Hzpickup, offset signals produced by the electrode itself, signalsproduced by the interaction of body fluids and the electrode gel, andlead wire and patient cable problems, general motion artefacts due torandom body movements or bad electrode-to-skin adhesion.

Skin (epidermis) stretching is the primary source of movement-relatedartefacts in vital body signs measurements (mainly electrical, but alsooptical, chemical). Studies have revealed that a voltage of severalmillivolts can be generated by stretching the epidermis, the outer layerof the skin. Compared to the intrinsic, inherent natural strain (skin isunder pre-tension), skin surface strains can become as high as 30-50%when skin is externally loaded or stretched. This type of artefact isfor instance visible as large baseline shifts and recurrent drifts inthe ECG signal occurring when the patient changes positions in bed, eatsor walks around. The epidermal artefact is the most troublesome of allmovement related artefacts because it is difficult to filterelectronically and its amplitude is often larger than the ECG signal.The most obvious solution to avoid motion related artefacts is doing themeasurement in a ‘still’ position by ensuring that the patient does notmove during the measurements. This is in practice however often notpossible, especially in diseased patients suffering from Parkinson(tremor), or when vital signs should be monitored continuously 24/7 orduring exercise/sports. Therefore many attempts have been made tocorrect for motion artefacts by sophisticated software algorithms andadaptive filtering, using multiple electrodes or additional sensingmodalities such as pressure, displacement, microphones, or opticalsensors, accelerometers, skin impedance measurement integrated in theelectrode to obtain contextual information or to correct for skin straininduced motion artefacts based on the detected amount of motion.

U.S. Pat. No. 6,912,414 B2 for instance discloses an electrode systemfor reducing noise from an electronic signal, the system including anelectrode that provides the electronic signal, and a motion sensor thatsenses motion and provides a motion signal. The electrode systemincludes a controller that determines a noise value based on an analysisof the motion signal, and subtracts the noise value from the electronicsignal. The electrode system can reduce or eliminate motion artefactfrom an electronic signal thus avoiding misdiagnosis, prolong proceduralduration and inappropriate treatment of a patient.

The drawback of this solution is the following: it involves complicatedalgorithms to subtract noises from measurement signal only aftermeasurement of the patient.

SUMMARY OF THE INVENTION

It is an object of the present invention to optimize the monitoring ofvital signs of a patient and reduce/minimize skin stretching basedsignal artefacts.

According to a first aspect of the invention, this object is realized bya vital sign monitoring system. The system comprises a segmented (and,for example, stretchable) electrode forming an in-plane electrode array(for example, arranged to allow for accommodating to skin-electrodestrain mismatch and strain measurement), wherein the electrode comprisesa skin adhering contact layer (for example, a skin contacting adheringlayer) mounted on a skin facing side of the electrode,

a deformation sensor arranged for identifying a deformation informationof the electrode and/or underlying skin,

a signal processor arranged to receive a vital sign signal from theelectrode and process the deformation information to remove artefactsfrom the vital sign signal, wherein the segmented electrode comprisesmultiple electrode segments and wherein the signal processor is arrangedto select that electrode segment that has a lowest deformation of allelectrode segments of the electrode.

The invention achieves the objective by selecting one or more electrodesegments that have the lowest (skin and/or electrode) deformation formeasurement thus selecting the signal with the least amount of artefactsfrom the multi-segmented electrode. The effect of deformation istherefore greatly reduced before sampling, thereby simplifying, or evenremoving the need for, the signal processing trying to compensate forthe artefacts after sampling.

In various embodiments, the signal processor may be arranged to measurethe vital sign signal using the selected electrode segment.

In various embodiments, the electrode may comprise either (semi-) rigidor stretchable, flexible sheet of material arranged to support themultiple electrode segments with respect to each other.

In various embodiments, the skin facing side of the electrode maycomprise an electrode backing material. In various embodiments, theelectrode backing material may comprise the multiple electrode segments.In various embodiments, the electrode may comprise either (semi-) rigidor stretchable, flexible sheet of material as the backing material.

A continuous measurement of skin deformation and analyzing the localskin strain field/strain distribution under the skin contactingelectrode by the deformation sensor allows the selection of an electrodesegment with little deformation. For example: a stretchable radiallyarrayed electrode has one or more integrated micro-cameras allowing oneto track skin deformation and derive associated strains using digitalimage correlation. The micro-camera or electrode may have an additionallight source to project random patterns onto the skin or a transparentskin adhesive to be able to improve image correlation quality. Usingsuitable data acquisition and image correlations algorithms and controlloops (multiplexing) one can continuously measure local in-plane strainsand switch between electrode segments to adapt to changing skin strainfields (body motion, or induced skin stretching), and read out electrodesegments associated with lines of non-extension (LoNE) to obtain‘deformation free’ vital sign signal.

The electrode are stick-to skin electrodes but also other sensingelectrode types (dry electrodes, textile electrodes, wet electrode) willbenefit from the proposed deformation measurement and electrodesegmentation. A deformation (skin extension) measurement and analysisenable to always select the best segment(s) to use to read out signalswith the least amount of skin stretching associated artefacts. Thismakes especially sense in stretch critical measurements, but having manysegments enables other correction and variance options. In the preferredembodiment the electrode is radially segmented.

Radially segmented (pie-shaped) electrode arrangement works particularlywell to cope with skin stretching induced artefacts. There is a physicaland mathematical reason for that, based on strain analysis andunderlying mechanical laws. FIG. 1 can be used as a graphicalrepresentation of a 2D state of strain subject to this invention.

The skin surface stretching is characterized by a planar bi-directionalstate of strain (or stress) in a small infinitesimal element of theelectrode area or the full electrode area. Such a state deformation orstrain is determined by two axial strains (Ex, Ey) and a shear strain(Exy), as shown in FIG. 1. Along the direction of so-called principalstrains (minimum and maximum strain), the contribution of shear strainis zero. Due to biaxial strain state, we have two principal strains (E1and E2); a compressive and a tensile one. The orientation of theprincipal strains can be calculated/determined by measuring axial andshear strains. These principal strains are orthogonally oriented to eachother but under a certain angle with respect to an x-y coordinate system(or Ex and Ey). As principal strains always cross each other there mustbe directions along with skin deformation is more or less zero.According to Oborpta and Newman, the Finite strain ellipse (FIG. 1) canbe used as a graphical representation of a 2D state of deformation andstrain. From principal strains, one can mathematically derive associatedlines of non-extension. From the principal strain directions thedirections of non-extension can be calculated where Φ is the anglebetween the principal strain and LoNE direction (FIG. 1). Note thatdirections of non-extension only exist if compression and tension areboth present. Mathematically this is when E1 and E2 have opposite signs.102 indicate the direction of two lines of non-extension as deformedellipse and undeformed circle intersect.

In a further embodiment the electrode forms concentric rings. Thoseembodiments are advantageous as the segments of electrode cover regionsof the skin, where virtually no deformations occur.

Similarly to radially segmented electrode segments, concentric rings areused to be able to read out directions of intersecting zero skindeformation (lines of non extension; LoNE) which are the result of twoprincipal strains.

The concept of deformation and motion of human skin states thatdeformations in an elastic body are described by a strain ellipsoid orellipse (FIG. 1), in which a small sphere of material deforms to nearlyellipsoidal shape under elastic deformation of the entire body. On thesurface of such an elastic body, the projected deformations transform asmall circle into an ellipse. Since all points on the ellipse arederived from points on the undeformed circle, in general, there may betwo directions in the ellipse that are not stretched. (They may be notedby superimposing the original circle on the deformed ellipse in FIG. 1)An extension and connection of these radial directions may be referredto as a mapping of the surface of the elastic body by lines ofnonextension. Skin is a soft composite tissue with non-linearviscoelastic material properties and responds to body movement via skinstretching. During body movement the skin is stretched as skin layersare firmly connected with each other and via fascia, muscle and tendonsattached to the skeleton. Therefore it is plausible to expect that skinstretching for example will cause changes in skin surface topography andsurface strain distribution from which signal artefact can arise. Thereis no direct physical interaction between segments and skin stretching.The number of segments and geometry is pre-defined; though only segmentsassociated with zero skin stretch are read out.

In a further embodiment the electrode comprise an skin adheringelectrode layer made of hydrogel, hygroscopic silicone gel adhesive orother medical grade skin adhesive such as polyurethane gel, acrylicadhesive, hydrocolloid, and related pressure sensitive adhesive.

In a further embodiment the electrode comprise stretchable, flexiblesheet of material. This embodiment is advantageous as it enablesdetecting a skin deformation, because the electrode can accommodate forskin-electrode strain mismatch and any deformation of the skin willresult in a deformation of the sensor material which can be measured.

In a further embodiment each electrode segment comprises a conductivecarbon-filled or conductive ionic (i.e., soap and carbon filled)silicone rubber (elastomer) and is further arranged to measuredeformation and identify deformation free electrode segments. Thisembodiment is advantageous as it enables detecting a skin deformation byadditionally integrating the deformation measurement function.Conductive silicone elastomer was developed by Philips and has beenshown to be very sensitive for example for pressure measurement;therefore it may be also used as strain measurement technology. In afurther embodiment the deformation sensor comprises a strain gauge, afibre optic sensor or a magnetic sensor. The deformation sensingtechnologies can be resistive, capacitive, optical, inductive ormagnetic. These measurement options all allow integration into theelectrode.

In a further embodiment the deformation sensor senses the deformation inat least two dimensions.

In a further embodiment the processor is further arranged to process thedeformation information based on a determination of the Line ofNon-extension (LoNEs). The concept of the Lines of Non-extension wasdeveloped by Arthur Iberall during research on the space suite. Hedescribed the Line of Non-extension (LoNEs) as contours along the humanbody where the skin does not stretch.

As it was explained above intersecting zero skin deformation (lines ofnon extension LoNEs; there are typically 2 LoNE axes; see also FIG. 1)are the result of two principal strains arising from a biaxial straincondition skin is subjected to. The reason why skin has bi-axial strainstate is because skin layers are firmly connected with each other andvia fascia, muscle, tendons attached to the bone/skeleton. Electrodesegments (electrode radially segmented and electrode form concentricrings) are used to be able to read out electrode segments associatedwith lines of non extension (LoNEs) and activate only these segmentswhich lie on contours along the human body where the skin does not oronly minimally stretch (LoNEs).

According to a second aspect of the invention, the objective is realizedby a method for a vital sign monitoring. A method comprises:identification of a deformation of an electrode comprising multipleelectrode segments by a deformation sensor, selecting at least oneelectrode segment that has lowest deformation of all electrode segments,measuring a vital sign signal using the selected electrode segment (orsegments).

In various embodiments, the method may comprise selecting at least oneelectrode segment that has lowest deformation of all electrode segmentsassociated with lines of non-extension, LoNEs, of the underlying softskin tissue.

According to a third aspect, there is provided a vital sign monitoringsystem comprising a deformation sensor configured to identifydeformation of a skin adhering electrode comprising multiple electrodesegments and a processor configured to select an electrode segment thathas a lowest deformation of all electrode segments associated with linesof non-extension, LoNEs, of the underlying soft skin tissue and measurea vital sign signal using the selected electrode segment.

According to a fourth aspect, there is a method of operating a vitalsign monitoring system that comprises a segmented electrode forming anin-plane electrode array. The electrode comprises a skin adheringcontact layer mounted on a skin facing side of the electrode. The methodcomprises identifying deformation information of the electrode,receiving a vital sign signal from the electrode and processing thedeformation information to remove artefacts from the vital sign signal.The segmented electrode comprises multiple electrode segments. Themethod also comprises selecting the electrode segment that has a lowestdeformation of all electrode segments of the electrode.

In various embodiments, the signal processor may be arranged to measurethe vital sign signal using the selected electrode segment.

In various embodiments, the electrode may comprise either (semi-) rigidor stretchable, flexible sheet of material arranged to support themultiple electrode segments with respect to each other.

In various embodiments, the skin facing side of the electrode maycomprise an electrode backing material. In various embodiments, theelectrode backing material may comprise the multiple electrode segments.In various embodiments, the electrode may comprise either (semi-) rigidor stretchable, flexible sheet of material as the backing material.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, similar reference characters generally refer to thesame parts throughout different views. Also, the drawings are notnecessarily to scale, with the emphasis instead generally being placedupon illustrating the principles of the invention.

FIG. 1 shows a graphical representation of a 2D deformation state, basedon the Finite Strain Ellipse method according to Obropta and Newman.

FIG. 2 shows a radially segmented (stretchable) electrode array andindicated example segments associated with Lines of Non-Extension.

FIG. 3a shows a radially segmented sensor array having strain gaugesincorporated therein.

FIG. 3b shows a cross section of the electrode according to theinvention.

FIG. 4 shows a vital sign measurement system.

FIG. 5 shows a schematic representation of a method according to thepresent invention.

FIG. 6 shows a segmented (stretchable) electrode array electrode withlongitudinal segments and a chessboard pattern.

FIG. 7 shows a segmented (stretchable) electrode array, whereinelectrode segments are concentric rings.

DETAILED DESCRIPTION OF EMBODIMENTS

Certain embodiments will now be described in greater details withreference to the accompanying drawings. In the following description,like drawing reference numerals are used for like elements, even indifferent drawings. The matters defined in the description, such asdetailed construction and elements, are provided to assist in acomprehensive understanding of the exemplary embodiments. In addition,well-known functions or constructions are not described in detail sincethey would obscure the embodiments with unnecessary detail. Moreover,expressions such as “at least one of”, when preceding a list ofelements, modify the entire list of elements and do not modify theindividual elements of the list.

FIG. 2 shows a radially segmented electrode sensor and two Lines of NoExtension. In this example, an electrode 100 comprises 16 multipleradially arrayed electrode segments, whereas segments 101 indicate skinstretching affected (‘deformed’) and 103 skin stretching unaffected(‘undeformed’) segments (FIG. 2).

Although the human skin is stretched during body motion, there isvirtually no stretch along the Lines of Non-extension (LoNEs) 102.

Since the human body tends to retain its form, taking no appreciable‘set’ after ordinary body deformations, its behavior is expected toconform to the laws of physical elasticity. Deformations in an elasticbody can be described by the strain ellipsoid, in which a small sphereof material deforms to nearly ellipsoidal shape under elasticdeformation of the entire body. On the surface of such an elastic body,the projected deformations transform a small circle into an ellipse.Since all points on the ellipse are derived from points on theundeformed circle, in general, there may be two directions in theellipse that are not stretched (They may be noted by superimposing theoriginal circle on the deformed ellipse.) An extension and connection ofthese radial directions may be referred to as a mapping of the surfaceof the elastic body by lines of non-extension.

During a measurement, electrode segments 103 will experience little orno deformation as they are positioned along the Line of no extension 102and the system will thus identify these as electrode segments that havea low deformation of all electrode segments and underlying skin. Theelectrode segment with the lowest deformation is subsequently selectedby the system to obtain an optimised skin-stretching artefact removedvital sign signal.

Radially segmented electrode arrangement works particularly as theyallow for greatest flexibility to read-out of segments associated withzero stretch (NoLE), because the angle between principal strains isnormally unknown (and not constant throughout the skin or body) andneeds to be measured for example with strain gauges. In a segmentedelectrode with longitudinal segments and a chessboard pattern (FIG. 6)only one read-out along one-line (one zero strain direction) would beaccurate. In this case, the electrode does not need to be a of circlesector shape (radially arrayed) but can be designed also in other wayshaving straight lateral segments throughout the circle area.

FIGS. 3 (a and b) depicts a radially segmented sensor having straingauges incorporated therein. An electrode 100 comprises a stretchableradially segmented electrode with 8 segments 101(103) and a strain gaugesensor 202. The skin adhering electrode layer (100) is placed on theskin (200) of the patient and is maintained on the skin with an skinadhering electrode layer 201 as shown in FIG. 3b . The ideal electrodematerial (and encapsulation material of the strain gauge) is made of anelastic material to conform to the skin and matching the skinproperties, i.e. one resembling the mechanical viscoelastic materialbehavior of skin. This can be for example a conductive ionic siliconemembrane electrode onto which strain gauges are mounted to measurestrains. Using suitable data acquisition and software algorithms andcontrol loops (multiplexing) one can continuously measure strainindicated by the various strain gages and switch the measurement betweenelectrode segments to adapt to changing skin deformations caused by(body motion, and read out that electrode segment where the lines ofnon-extension result in the least amount of deformation and thus a vitalsign signal with the lowest amount of artefacts caused by skindeformation). Strain gauges 202 (202 a, 202 b, 202 c) are placed on topof the stretchable electrode 101 (103). In a variant of this embodiment,the segments themselves can be used as strain (deformation) measurementsystem as a stretchable conductive carbon-filled silicone rubber(elastomer) is used as an electrode material so separate strain gaugesor other deformation measurements means are no longer needed. In anothervariant of this embodiment, an array of meander-structure metal wirescan be integrated in the bulk of the electrode and used as strainsensor.

There are at least 3 individual (separate) strain gauges 202 a, 202 b,202 c: two of the strain gauges should be placed at a 90 degree angle toeach other as two orthogonal strains such as Ex and Ey should bemeasured. The third one can be chosen randomly as it measures a shearstrain. If a rosette strain gauge is used, standardized configurationsare chosen.

In FIG. 3b a cross section of the electrode according to the inventionis shown. In this embodiment, strain gauges 202 are placed on top of thestretchable electrode 101(103). The skin adhering electrode layer (100)is placed on the skin (200) of the patient and is maintained on the skinwith an adhesive 201.

FIG. 4 depicts a vital sign measurement system showing a conceptualschematic describing the spatial selection of stretchable electrodesegments 101 (103). As shown in this example, the system 100 contains 16electrode segments 101. Each segment 101 is connected to an analogmultiplexer 305 which is controlled by a processor 303 (typically amicrocontroller). The processor 303 selects electrode segments 101 thatare being measured by the read out electronics 306. The read outelectronics comprises for instance sampling unit, amplification unit,and analog-to-digital conversion unit. The processor 303 estimates thedeformation level applied to each electrode based on the deformationmeasurements obtained from the strain gauges 202 that are shownseparately in FIG. 4 for clarity reasons but are actually as explainedin FIG. 3, part of the electrode sensor 100. The electrode segmentselection is then based on this estimation. The processor 303 can forexample select each electrode showing a strain lower than a certainthreshold value or select the one segment with the lowest deformationassociated. The specific and number of electrode segments that are beingselected can vary over time based on the deformation level variationsthat are being measured. The wearable device is therefore adapting itsmeasurements based on the specific body movement.

If the deformation on each electrode segment 101 is unknown, it maystill be possible to determine which of the segments are reportingreliable information based upon the fact that there are 2 LoNE axes. Forthis reason, if a sufficiently dense mesh of radial electrodes isdefined (must be radially spaced by at most half the closest anglebetween 2 LoNE axes), then there should be 2 sets of radial electrodesegments which qualitatively show the same or similar skin stretchingartefact reduced biosignal output (all others should show deviatingresults). In addition, analysis may allow identification of an artefactas it is a component of the signal and varies from segment to segment,reaching a minimum in one of the electrode segments. The electrodesegments thus found can be defined as the correct measurement. Again,criteria can be defined to reject measurements in situations whereeither difference between any 2 measurements exceeds a certain thresholdor radial electrodes with the same result are too close together to formthe 2 LoNE axes (i.e. if 2 adjacent electrodes indicate the same value).

In addition a calibration could be performed where the patient is askedto move through a series of motions while observing the resultingartefacts and identifying for the applied sensor which electrodesegments are positioned at a Line of No Extension.

In a further embodiment, concentric rings of electrode segments (FIG. 7)are used in order to account for non-uniform strains. For example, thesmaller the electrode segment (inner ring 103) the more likely that anarea of low strain may be measured, however at a lower signal accuracy.A larger electrode segment delivers higher quality measurement but ofcourse with a higher chance of artefacts introduced by deformation.Again, comparisons between smaller (103) and larger (101) electrode ringsegments can considered.

Another embodiment of a vital sign monitoring system according to thepresent invention is a combination of the deformation measurement forexample using a strain gauge with electrode segments output signals tomake the identification of zero-stretch electrode segments morerobust/reliable. An alternative to this embodiment is to excludeelectrode segments with signal levels above a certain threshold (i.e.above typical physiological signal levels). This processing step shouldbe applied after having filtered out common-mode interferences (e.g.50/60 Hz).

The method according to the invention is depicted in FIG. 5.Specifically, in FIG. 5a after beginning of the vital sign measurementin step 401 by the vital sign monitoring system, the next step 402 isthe identification of a deformation of an electrode comprising multipleelectrode segments by the system using a deformation sensor. Then instep 403 the system selects that electrode segment that has a lowestdeformation of all the segments of that electrode and using the selectedelectrode segment start measuring a vital sign signal of the patient(404). Then subsequently the vital sign signal of the patient is stored(405). FIG. 5b shows alternative version of method according toinvention. A loop from step 405 back to step 402 so that the deformationinformation is again obtained and the selection changed if anotherelectrode segment turns out to be more optimal.

While several inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariation of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited. Also, reference numerals appearing in the claims in parenthesesare provided merely for convenience and should not be viewed as limitingin any way.

The invention claimed is:
 1. A vital sign monitoring system comprising:an electrode forming an in-plane electrode array, wherein the electrodecomprises a plurality of electrode segments and a skin adhering contactlayer mounted on a skin facing side of the electrode; a deformationsensor arranged for identifying deformation information indicatingrespective deformations of the plurality of electrode segments of theelectrode; and a signal processor programmed to receive a vital signsignal from the electrode, to process the deformation information toselect an electrode segment of the plurality of electrode segments thathas a lowest deformation of the plurality of electrode segments, and tomeasure the vital sign signal using the selected electrode segment toreduce artefacts from the vital sign signal.
 2. The system of claim 1,wherein the electrode is radially segmented.
 3. The system of claim 1,wherein the plurality of electrode segments form concentric rings. 4.The system of claim 1, wherein the electrode further comprises a skinadhering electrode layer made of hydrogel, hygroscopic silicone geladhesive, a polyurethane gel, an acrylic adhesive, a hydrocolloid. 5.The system of claim 1, wherein the electrode further comprises a (semi-)rigid or stretchable, flexible sheet of material arranged to support theplurality of electrode segments with respect to each other.
 6. Thesystem of claim 1, wherein each electrode segment of the plurality ofelectrode segments comprises conductive carbon-filled silicone rubberand is arranged for identifying the deformation information.
 7. Thesystem of claim 1, wherein the deformation sensor comprises: a straingauge, a fibre optic sensor, a magnetic sensor, or a micro-camera. 8.The system of claim 1, wherein the deformation sensor senses thedeformation of the electrode in at least two dimensions.
 9. The systemof claim 1, wherein the processor is further programmed to process thedeformation information based on a determination of Lines ofNon-extension (LoNEs).
 10. A vital sign monitoring system comprising: anelectrode comprising a plurality of stretchable electrode segments and askin adhering layer configured to adhere the electrode to skin of apatient; a deformation sensor configured to determine deformations ofthe plurality of stretchable electrode segments of the electrode; and asignal processor programmed to select at least one electrode segment ofthe plurality of stretchable electrode segments that has a lowestdeformation of the plurality of electrode segments based on thedetermined deformations of the plurality of stretchable electrodesegments, and to measure a vital sign signal indicating a vital sign ofthe patient using the at least one selected electrode segment.
 11. Thesystem of claim 10, wherein the plurality of stretchable electrodesegments are radially segmented.
 12. The system of claim 10, wherein theplurality of stretchable electrode segments comprise elastic materialconfigured to conform to the skin of the patient and to match propertiesof the skin.
 13. A method for a vital sign monitoring comprising:identifying a deformation of a skin adhering electrode comprising aplurality of electrode segments by a deformation sensor, wherein theplurality of electrode segments are deformable; selecting an electrodesegment of the plurality of electrode segments that has a lowestdeformation of the plurality of electrode segments associated with linesof non-extension (LoNEs) of underlying soft skin tissue; and measuring avital sign signal using the selected electrode segment.
 14. The methodof claim 13, wherein the electrode comprises a stretchable, flexiblesheet of material.
 15. The method of claim 13, wherein the electrode isradially segmented.
 16. The method of claim 13, wherein the plurality ofelectrode segments are arranged in concentric rings.
 17. The method ofclaim 13, wherein the plurality of electrode segments are arrangedlongitudinally.
 18. The system of claim 1, wherein the plurality ofelectrode segments are arranged longitudinally.
 19. The system of claim1, wherein the plurality of electrode segments are arranged in achessboard pattern.
 20. The method of claim 13, wherein the plurality ofelectrode segments are arranged in a chessboard pattern.